Which waveform features are commonly seen with severe turbulence following high-grade stenosis?

• A. Serration of peak velocity envelope with fill-in of the spectral window and bright lower portions
• B. Smooth peak velocity envelope with a clean spectral window
• C. No turbulence and a flat spectral display
• D. Low flow with a narrowed spectral window

Answer: (A)

Post-stenotic turbulence from a high-grade narrowing causes the flow to become chaotic as eddies form downstream. That chaotic flow shows up on the Doppler spectrum as a broadened, irregular envelope rather than a neat, smooth one. The peak velocity envelope becomes serrated because velocities repeatedly rise and fall as vortices mix with the forward flow. The spectral window fills in because a wide range of velocities occurs at any moment, not just the highest speed at peak systole. Energy is present at lower velocities too, so those portions of the spectrum appear brighter or more filled in.

In contrast, a smooth, clean envelope with a well-defined spectral window points to laminar flow without turbulence. No turbulence would yield a flat or very quiet spectrum, and low flow with a narrowed window wouldn’t reflect the extensive velocity fluctuations seen with turbulence after severe stenosis.